Insights into magmatic evolution and recharge history in Capraia Volcano (Italy) from chemical and isotopic zoning in plagioclase phenocrysts

TY - JOUR

T1 - Insights into magmatic evolution and recharge history in Capraia Volcano (Italy) from chemical and isotopic zoning in plagioclase phenocrysts

AU - Gagnevin, D.

AU - Waight, Tod Earle

AU - Daly, J.S.

AU - Poli, G.

AU - Conticelli, S.

PY - 2007

Y1 - 2007

N2 - Plagioclase phenocrysts in dacites from the high-K calc-alkaline CapraiaVolcano were investigated for major, trace element and Sr isotope variations in order to gain better insight into the proposed open-system behaviour of the volcano. Repeated dissolution zone in plagioclases from the early-erupted Monte Castello (MC) and later Monte Rucitello (MR) dacitic units are associated with a sharp increase in An content and variation in isotopic compositions (87Sr/86Sr=0.70872-0.71004), which argue for repeated magma mixing. In particular, petrographic and mineralogical evidence suggest that recharge with hot, basaltic magma occurred repeatedly during the lifetime of the Capraia volcanic system. We attempted to correlate shared crystallization and resorption histories using chemical (mol% An, Fe) and Sr isotopic zoning in plagioclase. In this correlation framework, the observed mismatch between chemical and isotopic data in some phenocrysts is interpreted to reflect either growth of phenocrysts in a separate magma chamber, or compositional zoning within a single magma chamber. A minor role of crustal contamination is inferred. Instead, the intra-crystal variations in isotopic composition in plagioclase reflect the existence of distinct components that may have thoroughly mixed at the end of the MC plagioclase growth history. The dominant radiogenic component is similar to lamproites occurring in Tuscany. Recharge with this component occurred throughout the genesis of the MR dacites, but was restricted to the early growth history of the MC dacites. The MR plagioclases are inferred to have crystallized from separate, more differentiated batches of magma that were likely to have evolved at the top of a zoned magma reservoir. Decrease in the An content after most dissolution zones in all phenocrysts, and low temperature estimates from zircon saturation thermometry (800 °C) also emphasize the importance of crystal fractionation during the evolution of the volcano, in agreement with the occurrence of a significant amount of rhyolitic material. Thus, it is inferred that a rather large magma chamber may have existed during the first cycle of eruptive activity.

AB - Plagioclase phenocrysts in dacites from the high-K calc-alkaline CapraiaVolcano were investigated for major, trace element and Sr isotope variations in order to gain better insight into the proposed open-system behaviour of the volcano. Repeated dissolution zone in plagioclases from the early-erupted Monte Castello (MC) and later Monte Rucitello (MR) dacitic units are associated with a sharp increase in An content and variation in isotopic compositions (87Sr/86Sr=0.70872-0.71004), which argue for repeated magma mixing. In particular, petrographic and mineralogical evidence suggest that recharge with hot, basaltic magma occurred repeatedly during the lifetime of the Capraia volcanic system. We attempted to correlate shared crystallization and resorption histories using chemical (mol% An, Fe) and Sr isotopic zoning in plagioclase. In this correlation framework, the observed mismatch between chemical and isotopic data in some phenocrysts is interpreted to reflect either growth of phenocrysts in a separate magma chamber, or compositional zoning within a single magma chamber. A minor role of crustal contamination is inferred. Instead, the intra-crystal variations in isotopic composition in plagioclase reflect the existence of distinct components that may have thoroughly mixed at the end of the MC plagioclase growth history. The dominant radiogenic component is similar to lamproites occurring in Tuscany. Recharge with this component occurred throughout the genesis of the MR dacites, but was restricted to the early growth history of the MC dacites. The MR plagioclases are inferred to have crystallized from separate, more differentiated batches of magma that were likely to have evolved at the top of a zoned magma reservoir. Decrease in the An content after most dissolution zones in all phenocrysts, and low temperature estimates from zircon saturation thermometry (800 °C) also emphasize the importance of crystal fractionation during the evolution of the volcano, in agreement with the occurrence of a significant amount of rhyolitic material. Thus, it is inferred that a rather large magma chamber may have existed during the first cycle of eruptive activity.

KW - Faculty of Science

KW - petrologi

KW - Capraia vulkanen

KW - plagioclase

KW - petrology

KW - phenocrysts

KW - plagioclase phenocrysts

KW - Capraia volcano

U2 - 10.1016/j.jvolgeores.2007.07.018

DO - 10.1016/j.jvolgeores.2007.07.018

M3 - Journal article

SN - 0377-0273

VL - 168

SP - 28

EP - 54

JO - Journal of Volcanology and Geothermal Research

JF - Journal of Volcanology and Geothermal Research

IS - 1-4

ER -